I still love my Neuma Hybrids, they run like a dream. Line, color and put in black and gray so smooth. But I only ran them on air. The electric thing is a total piece of junk. I started a tattoo with it once and put the air back on after a few min. The electric thing needs to be run around 14+ volts to work. Advice from Neuma's site (when it was up) said to run @ 13-18v. It said don't be affraid to crank it up.
If it wasn't for the noise I would still be using them (with air) all day/every day.